In recent years, as a control unit for controlling an arc welding robot, there has been employed a control unit of a type having a built-in welding machine, in order to improve the operation environment thereof, reduce the installation space thereof, simplify the connection between the welding machine and robot, make it easy to use, and enhance the maintenance thereof (see the patent literature 1, for example).
FIG. 4 shows the above-mentioned control unit for controlling an arc welding robot with a built-in welding machine. In FIG. 4, reference character 41 designates a storage case for storing therein a robot controller unit and a welding power supply in an integral manner, while the storage case 41 is divided to two stages by an electromagnetic shield plate 42. With the electromagnetic shield plate 42 as the boundary thereof, the lower stage is used as a storage portion for storing an arc welding power supply 44 therein, whereas the upper stage is used as a storage portion for storing a robot controller unit 43 therein. In this manner, since the robot controller unit 43 and arc welding power supply 44 are stored in the same storage case, not only the arc welding robot control unit can be made easy to handle but also the installation space thereof can be reduced greatly
Also, as a robot control unit, there has been employed a robot control unit of a type which, in order to secure safety in the maintenance operation thereof, can cut off power supply to the servo amplifier of the robot using an emergency stop signal (see the patent literature 2, for example).
FIG. 5 shows the above-mentioned conventional robot control unit. Specifically, in a box body 52 of a robot control unit 51 connected to a robot movable part 50, there is provided a door interlock switch 53. The door interlock switch 53, when the panel 52a of the box body 52 is removed, outputs an emergency stop signal to a contact circuit (not shown) for controlling the energization of a coil R1 to thereby de-energize the coil R1. Owing to this, contacts r1a, r1b are opened and the power supply to a coil R2 is cut off, so that the coil R2 is also de-energized. And, contacts 54a to 54c within an electromagnetic contact device 54 are opened respectively to cut off the power supply to a servo amplifier 56 from a power supply 55, thereby stopping the driving of a servo motor provided in the robot movable part 50.
In this manner, in the maintenance operation, the robot movable part 50 can be made immovable.    Patent literature: JP 2674358 publication (FIG. 1)    Patent literature: JP Hei-7-256585 publication (FIG. 1)